The present invention refers in general to a hybrid propulsion system for a motor vehicle comprising an internal combustion engine, an electric machine and a double-clutch transmission provided with a mechanical gearbox. More particularly, the invention relates to the subsystem formed by the electric machine and the gearbox of the double-clutch transmission of the hybrid propulsion system defined above.
US2005/139035 discloses a hybrid propulsion system for a motor vehicle comprising an internal combustion engine, an electric machine and a double-clutch transmission, wherein the double-clutch transmission comprises a clutch unit and a mechanical gearbox having a pair of coaxial primary shafts intended to be torsionally coupled each with a drive shaft of the internal combustion engine of the motor vehicle by means of a respective friction clutch of the clutch unit, as well as a secondary shaft and a lay shaft both arranged parallel to the two primary shafts, and wherein the electric machine is permanently cinematically connected to either of the two primary shafts of the gearbox via a gear train including a pinion mounted on an output shaft of the electric machine, at least one intermediate gearwheel and a gearwheel which is mounted on the aforesaid primary shaft of the gearbox and acts as driving gearwheel of a gear train associated to one of the gears of the gearbox.